A major objective of the proposed investigation will be to document the timing of formation and migration of neural crest cells in intact, living embryos of the zebrafish (Brachydanio rerio). The behavior of individual neural crest cells in vivo will be recorded by time-lapse cinematography at cranial and trunk levels. Observations of living cells will be correlated with SEM and TEM analysis of the same and/or related cells. The extracellular matrix associated with migrating neural crest cells will be characterized by histochemical and cytochemical techniques. The results of these studies will provide a morphological basis for comparing the behavior of neural crest cells in this teleost with that in higher vetebrates, and will indicate the feasibility for directly observing the effects of teratogenic agents on neural crest cells which may result in abnormal development, particularly in the cranio-facial region. As a correlated study of cell behavior in situ, the behavior of cells at the undersurface of the zebrafish blastoderm during gastrulation and formation of the embryonic shield will also be recorded in vivo by time-lapse cinematography and combined with subsequent SEM and TEM observations of the same cells. The ultrastructural observations of the zebrafish gastrula will be compared with similar SEM and TEM analyses of gastrulation in the trout embryo. These studies will provide currently unavailable information regarding these important morphogenetic movements during teleost embryogenesis.